Lee Byrne will miss Wales's first Six Nations match, against England at Twickenham next Saturday, after he was banned for two weeks for re-entering the field without permission during the Ospreys' Heineken Cup victory over Leicester in Swansea last weekend. The full-back had pleaded guilty to a charge of misconduct.

The Ospreys were fined €25,000 (£21,683) after they, too, pleaded guilty to misconduct. They will meet Biarritz in a Heineken Cup quarter-final on 10 April. Leicester had demanded a replay, arguing that Byrne, who returned to the field after receiving treatment for a cut toe, had thwarted a try-scoring chance in the 50 seconds in which was a 16th man.

Byrne and the Ospreys had their cases heard by an independent judicial panel in Dublin today. The hearing was ordered by Roger O'Connor, European Rugby Cup Ltd's disciplinary officer, after a two-day investigation prompted by an official complaint from Leicester. It was the first time a player had been called to account after a team had been caught with 16 men on the field. While the three-man panel accepted there had been no premeditated attempt to cheat and dismissed ­Leicester's claim that Byrne's presence had a material impact on the final result, it said: "Mr Byrne re-entered the pitch without the referee's permission and he knew or ought to have known that he needed that permission.

"The committee found that this represented a clear breach of the ­substitution protocol, which forms part of the Heineken Cup tournament rules, and that the club could have done more to ensure that such a breach did not occur. However, the committee found that the breach had not been deliberate or premeditated on the part of the club's management and that there had been no material effect on the match."

A one-week ban would have amounted to nothing for Byrne because he was not in the Ospreys' squad for tonight's LV Cup match against the Newport Gwent ­Dragons. His unavailability is a significant blow for the Wales coach, Warren Gatland, who does not have a specialist replacement in his squad.

Byrne has the right to appeal, as do the Ospreys, who declined to comment on the punishment.

Wales will on Sunday announce their side to face England on 6 February and any new hearing would not take place until at least Monday. Leicester are not allowed to appeal but ERC is. The governing body's only grounds for doing so would be if it agreed with the Tigers that Byrne's reappearance had a material impact on the result and that the Ospreys should have been given more than a fine.